Q: Engine puffs blue smoke; thumping noise at highway speeds

asked by on September 07, 2016

In the mornings when I start my SUV, for a few seconds the engine puffs blue smoke. When I’m driving on the highway at 60 mph, it begins to make a very obnoxious thumping sound that can also be felt by the vibrations. It feels like there is something stuck to the tire, but when I examine them, I don’t find anything. With more speed, the louder it becomes. I have looked at the transmission, driveline, shafts - all seem fine. Another problem is that when I am braking, the steering wheel shakes and there is a loud noise under the brake pedal. I have already changed the brake pads and the rotors, machined them, etc. No repairs have worked! I would greatly appreciate your advice on what will fix my car. Thanks.

Hi there, thanks for asking about your 2004 Infiniti FX45. The blue smoke you notice on initial start-up is likely caused by worn exhaust valve stem seals. They allow a tiny amount of oil to get into the combustion chamber while the car sits overnight. This will slowly get worse with additional miles until the valve stem seals are replaced. Have the front tires and wheels checked for balance, "roundness", or any separation of the tread of the tire at a reputable tire dealer. There is likely something amiss that’s showing up at highway speed and under braking. If you want to have this checked by a certified mechanic, a technician from YourMechanic can come to your home or office to inspect the smoke coming from your car’s exhaust.

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